Distribution, Variability of Seeps

Abstract

Various cold seep systems and related gas hydrate accumulations have been discovered in the South China Sea over the past two decades. Based on high-resolution seismic data, subbottom profiles, in-situ observations, deep drilling and coring, and hydrate gas geochemical analysis, the geological and geophysical characteristics of these cold seep systems and their associated gas hydrate accumulations in the Qiongdongnan Basin, Shenhu area and Dongsha area in the Pearl River Mouth Basin, Taixinan Basin, and Beikang Basin were investigated. Cold seep systems are present at different stages of evolution and exhibit various seabed microgeomorphic, geological, and geochemical features. Active cold seep systems with notable gas leakage, gas plumes, and microbial communities and inactive cold seep systems with authigenic carbonate pavements are related to the variable intensity of the gas-bearing fluid, which is usually derived from deep strata through mud volcanoes, mud diapirs, gas chimneys, and faults. This indicates a paragenetic relationship between the gas-bearing fluid and the seafloor morphology of cold seeps and deep-shallow coupling of gas hydrates, cold seeps, and deep petroleum reservoirs in the South China Sea.